Elongate implantable carrier member having an embedded stiffener

ABSTRACT

An apparatus including a flexible elongate carrier member configured to introduce a therapeutic element into the recipient and a stiffening member, permanently embedded in and longitudinally extending through at least a first region of said carrier member, configured to decrease said flexibility of said carrier member region so as to prevent deformation of said first region during implantation into the recipient.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 12/065,209 filed Oct. 14, 2008, now U.S. Pat. No.8,249,724, which claims priority from AU Provisional Application2005904743, entitled, “A Cochlear Implant Electrode Array,” filed Aug.31, 2005, and U.S. Provisional Patent Application No. 60/748,273,entitled “Electrode Carrier Member Having An Embedded Stiffener for aProsthetic Hearing Implant,” filed Dec. 8, 2005, which are herebyincorporated by reference herein.

BACKGROUND

1. Field of the Invention

The present invention relates generally to stimulating medical devicesand, more particularly, to an elongate implantable carrier member havingan embedded stiffener.

2. Related Art

Hearing loss is generally of two types, namely conductive andsensorineural. Conductive hearing loss occurs when the normal mechanicalpathways for delivering sound to the hair cells in the cochlea areimpeded, for example, by damage to the ossicles. In such cases, hearingloss may often be improved by the use of conventional hearing aids,which amplify sound so that acoustic information reaches the cochlea andthe hair cells. Such hearing aids utilize acoustic mechanicalstimulation whereby sound is amplified according to a number of varyingtechniques, and delivered to the inner ear as mechanical energy. Thismay be through a column of air applied to the eardrum, or through thedelivery of direct mechanical forces to the ossicles of the middle ear.

Sensorineural hearing loss, however, is due to the absence ordestruction of the hair cells in the cochlea which are needed totransduce acoustic signals into auditory nerve impulses. Individualssuffering from this type of hearing loss are unable to derive anybenefit from conventional hearing aids regardless of the volume of theacoustic stimulus. This is because the natural mechanisms fortransducing sound energy into auditory nerve impulses have been damaged.In such cases, Cochlear™ implants (also referred to as Cochlear™devices, Cochlear™ prostheses, Cochlear™ implant systems, and the like;simply “cochlear implants” herein) have been developed to provide thesensation of hearing to such individuals. In cochlear implants,electrical stimulation is provided via stimulating electrodes positionedas close as possible to the nerve endings of the auditory nerve,essentially bypassing the hair cells in a normally functioning cochlea.The application of a stimulation pattern to the nerve endings causesimpulses to be sent to the brain via the auditory nerve, resulting inthe brain perceiving the impulses as sound.

The treatment of both of the noted types of hearing loss has been quitedifferent, relying on two quite different principles to deliver signalsto be perceived by the brain as sound. It is relatively common inhearing impaired individuals to experience sensorineural hearing lossfor sounds in the high frequency range, and yet still be able to discernsounds in the middle to low frequency range, either through the use of aconventional hearing aid, or naturally. Traditionally, in the majorityof such cases, the recipient would only receive treatment to preserveand improve the hearing for the middle to low frequency sounds, mostprobably via a conventional hearing aid, and little would be done toattempt to restore the hearing loss for the high frequency sounds. Thisis due to the potential trauma caused by the implantation of anelectrode assembly into the cochlea. Only if the individual lost theability to perceive middle to low frequency sounds would considerationthen be given to restoring the hearing loss for the high frequencysounds, in which case a cochlear implant would be considered a possiblesolution.

More recently, there has been an increased interest inElectro-Acoustical Stimulation (EAS) in which electrical stimulation ofthe cochlea is used in conjunction with acoustical stimulation. This hasresulted in the development of various electrode assemblies that aredesigned to be as atraumatic to residual hearing as possible.

SUMMARY

In one aspect of the present invention an apparatus is disclosed. Theapparatus comprises: a flexible elongate carrier member configured tointroduce a therapeutic element into the recipient; and a stiffeningmember, permanently embedded in and longitudinally extending through atleast a first region of said carrier member, configured to decrease saidflexibility of said carrier member region so as to prevent deformationof said first region during implantation into the recipient. Theapparatus may be an electrode assembly for implanting electrodes in therecipient's cochlea.

In another aspect of the present invention, a cochlear implant isdisclosed. The cochlear implant comprises: a speech processor forprocessing received sounds to generate coded stimulation controlsignals; a stimulator unit configured to generate stimulation signals inresponse to said control signals; and an electrode assembly. Theelectrode assembly in turn comprises: a flexible elongate carrier memberhaving a plurality of electrodes disposed on thereon, said electrodesconfigured to stimulate auditory nerves of the recipient's cochlea; anda stiffening member, permanently embedded in and longitudinallyextending through at least a first region of said carrier member,configured to decrease said flexibility of said carrier member region soas to prevent deformation of said first region during implantation intothe recipient.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an implanted cochlear implant suitablefor implementing embodiments of the present invention;

FIG. 2A is a side view of an electrode assembly in accordance with oneembodiment of the present invention shown prior to insertion into acochlea;

FIG. 2B is a side view of the electrode assembly illustrated in FIG. 2A,shown after insertion into a cochlea;

FIG. 2C is a cross sectional view of the electrode assembly of FIGS. 2Aand 2B taken along section line 2C-2C in FIG. 2A;

FIG. 2D is a cross sectional view of the electrode assembly of FIGS. 2Aand 2B taken along section line 2D-2D in FIG. 2A;

FIG. 2E is a cross sectional view of the electrode assembly of FIGS. 2Aand 2B taken along section line 2E-2E in FIG. 2A;

FIG. 3A is a side view of one embodiment of a stiffening element of thepresent invention suitable for implementation in the carrier memberillustrated in FIGS. 2A-2E;

FIG. 3B is a side view of another embodiment of a stiffening element ofthe present invention suitable for implementation in the carrier memberillustrated in FIGS. 2A-2E; and

FIG. 3C is a side view of a further embodiment of a stiffening elementof the present invention suitable for implementation in the carriermember illustrated in FIGS. 2A-2E.

DETAILED DESCRIPTION

Embodiments of the present invention are generally directed to anapparatus and method for facilitating the temporary or permanentimplantation of a therapeutic element into a patient. Embodiments of thepresent invention are described below in connection with one type ofmedical device, a cochlear implant. Cochlear implants use directelectrical stimulation of auditory nerve cells to bypass absent ordefective hair cells that normally transduce acoustic vibrations intoneural activity. Such devices generally use electrodes inserted into thescala tympani of the cochlea so that the electrodes may differentiallyactivate auditory neurons that normally encode differential pitches ofsound. Such devices are also used to treat a smaller number of patientswith bilateral degeneration of the auditory nerve. For such patients,the cochlear implant provides stimulation of the cochlear nucleus in thebrainstem.

Exemplary embodiments of the present invention are described herein inconjunction with a exemplary cochlear implant such as a Contour™,Freedom™, Nucleus™ or Cochlear™ implant sold by Cochlear Limited,Australia. Such devices are described in U.S. Pat. Nos. 4,532,930,6,537,200, 6,565,503, 6,575,894, and 6,697,674, which are herebyincorporated by reference herein. It should be understood to those ofordinary skill in the art that embodiments of the present invention maybe used in other stimulating medical devices such as other types ofprosthetic hearing implants, neurostimulators, cardiacpacemakers/defibrillators, etc. as well as other medical devices whichutilize an elongate carrier member to temporarily or permanentlyimplant, deliver or otherwise introduce a therapeutic element such as aninert or pharmacological agent, sensor, device, etc, into a recipient.

FIG. 1 is a cut-away view of the relevant components of outer ear 101,middle ear 102 and inner ear 103, which are described next below. In afully functional ear, outer ear 101 comprises an auricle 105 and an earcanal 106. An acoustic pressure or sound wave 107 is collected byauricle 105 and channeled into and through ear canal 106. Disposedacross the distal end of ear cannel 106 is a tympanic membrane 104 whichvibrates in response to acoustic wave 107. This vibration is coupled tooval window or fenestra ovalis 110 through three bones of middle ear102, collectively referred to as the ossicles 111 and comprising themalleus 129, 112, the incus 113 and the stapes 114. Bones 112, 113 and114 of middle ear 102 serve to filter and amplify acoustic wave 107,causing oval window 110 to articulate, or vibrate. Such vibration setsup waves of fluid motion within cochlea 132. Such fluid motion, in turn,activates tiny hair cells (not shown) that line the inside of cochlea132. Activation of the hair cells causes appropriate nerve impulses tobe transferred through the spiral ganglion cells and auditory nerve 116to the brain (not shown), where they are perceived as sound. In personsexperiencing sensorineural hearing loss, there is an absence ordestruction of the hair cells. Oftentimes, a cochlear implant isutilized to directly stimulate the spinal ganglion cells to provide ahearing sensation to such persons.

FIG. 1 also shows how an exemplary cochlear implant 120 is positioned inrelation to outer ear 101, middle ear 102 and inner ear 103. Prosthetichearing implant 120 comprises external component assembly 122 which isdirectly or indirectly attached to the body of the recipient, and aninternal component assembly 124 which is temporarily or permanentlyimplanted in the recipient. External assembly 122 comprises microphone125 for detecting sound which is outputted to a BTE (Behind-The-Ear)speech processing unit 126. During use, microphone 125 is preferablyworn on the pinna of the recipient, however, other suitable locationsmay be envisaged, such as a lapel of the recipient's clothing. Speechprocessing unit 126 generates coded signals which are provided to anexternal transmitter unit 128, along with power from a power source suchas a battery.

External transmitter unit 128 comprises an external coil 130 and,preferably, a magnet (not shown) secured directly or indirectly inexternal coil 130. Internal components 124 comprise an internal receiverunit 132 having an internal coil (not shown) that receives and transmitspower and coded signals from external assembly 122 to a stimulator unit134 to apply the coded signal along an electrode assembly 140. Electrodeassembly 140 enters cochlea 132 at cochleostomy region 142 and has oneor more electrodes 150 is positioned to substantially be aligned withportions of tonotopically-mapped cochlea 115. Signals generated bystimulator unit 134 are applied by the electrodes 150 of electrode array144 to cochlea 132, thereby stimulating auditory nerve 116. It should beappreciated that although in the embodiment shown in FIG. 1 electrodes150 are arranged in an array 144, other arrangements are possible.

Electrode assembly 140 should assume an optimal electrode position incochlea 132 upon or immediately following implantation into the cochlea.It is also desirable that electrode assembly 140 be configured such thatthe insertion process causes minimal trauma to the sensitive structuresof the cochlea. Usually an electrode assembly is held in a straightconfiguration at least during the initial stages of the insertionprocedure, conforming to the natural shape of the cochlea during andsubsequent to implantation.

While cochlear implant system 100 is described as having externalcomponents, in another embodiment, the controller, including themicrophone, speech processor and power supply, may also be implantable.In such embodiments, the controller may be contained within ahermetically sealed housing or the housing used for stimulator unit 134.

FIG. 2A is a side view of an electrode assembly 200 in accordance withone embodiment of the present invention shown prior to insertion into acochlea. FIG. 2B is a side view of electrode assembly 200 shown afterinsertion into a cochlea. FIGS. 2C-2E are cross sectional views ofelectrode assembly 200 taken along their respective section linesillustrated in FIG. 2A.

Electrode assembly 200 comprises a carrier member 202, a collar member204, a holding member 1212 and lead 214. Carrier member 202 has a distalend or tip region 210 and a proximal end 228 connected tolaterally-extending collar member 204. The opposing end of collar member204 is connected to holding member 1212. A lead 214 longitudinallyextends through carrier member 202, collar member 204 and holding member1212 to electrically connect electrodes 150 with an external device suchas receiver/stimulator unit 134 (FIG. 1).

When implanted in a recipient, the longitudinally-extending surface ofcarrier member 202 which faces the interior of cochlea 132 is referredto herein as the medial surface 216 of carrier member 202. The opposingside of carrier member 202, referred to herein as lateral surface 218,faces the external wall and bony capsule (not shown) of cochlea 132. Itshould be understood that the terms medial surface, medial direction andthe like are generally used herein to refer to the surfaces, featuresand directions toward the center of cochlear 132, while the termslateral surface, lateral direction and the like are generally usedherein to refer to surfaces, features and directions toward the exteriorof cochlea 132.

A plurality of spaced-apart electrodes 212 are mounted on or in carriermember 202. Electrodes 212 may be disposed in a linear or non-lineararray on or in carrier member 202, and may be positioned to align withpredetermined regions of tonotopically mapped cochlea 132. In onealternative embodiment, electrodes 212 have variable spacing asdescribed in U.S. Provisional Patent Applications 60/748,217,60/748,274, and 60/748,314, which are hereby incorporated by referenceherein. Such arrangements allow for individual electrodes 212 to beenergized to stimulate selected regions of cochlear 132.

In one embodiment, electrodes 212 are half-band electrodes disposed onmedial surface 216 of carrier member 202. It should be appreciated,however, that any electrodes now or later developed suitable for aparticular application or therapeutic objective may be used inalternative embodiments of the invention. For example, in onealternative embodiment, electrodes 212 are banded electrodes extendingsubstantially around carrier member 202. In another alternativeembodiment, electrodes 212 do not laterally extend to or around theedges of carrier member 202.

Typically, each electrode 212 is arranged orthogonal to longitudinalaxis 250 of carrier member 202. It should be appreciated, however, thatother relative positioning and orientations may be implemented inalternative embodiments. It should further be appreciated that thequantity of electrodes 212 may vary from as few as one or two to as manyas twenty-four or more.

In certain embodiments, at least one electrode 212 has a surface that isat least adjacent medial surface 216 of carrier member 202. Preferably,one or more electrodes 212 has a surface that is collocated with medialsurface 216 of carrier member 202. In another embodiment, the surfacesof electrodes 212 are raised above or recessed into medial surface 216of carrier member 202.

Electrodes 212 may be manufactured from a biocompatible conductivematerial such as platinum, although other materials or combinations ofmaterials may be used. Alternatively, electrodes 212 may be coated witha biocompatible covering that does not substantially interfere with thetransfer of stimulation signals to cochlear 132.

Each electrode 212 is electrically connected to at least one multi- orsingle-filament wire 252 that is embedded within flexible carrier member202, collar member 204, handle member 212 and lead 214. As shown in FIG.2D, in some embodiments wires 252 are embedded in the volumetric core254 of carrier member 202. In collar member 204, shown in FIG. 2C,stiffening member 208 and wires 252 extend or travel through a centralvolumetric core 256. In an alternative embodiment, wires 252 may belocated at or near surface 216 and/or surface 218 of carrier member 202.In other embodiments, wires 252 are embedded in different regions ofcarrier member 202 to facilitate attainment of a desired curvature, tomaintain orientation of carrier member 202 once it is implanted, toattain a desired level of isolation between stiffening member 208 andwires 252, and/or to achieve other objectives. It is through wires 252that stimulator/receiver unit 134 (FIG. 1) provides electrical stimulito electrodes 212. In one embodiment, wires 252 are connected toelectrodes 212 by welding, although any suitable connecting means now orlater developed may be used.

It should be appreciated that the quantity of wires 252 connected toeach electrode 212 may vary. For example, in one alternative embodiment,at least two electrically conducting wires 252 are connected to each ofone or more electrodes 212. It should also be appreciated that suitabletransmission means other than filament wires may be used to communicablycouple receiver/stimulator unit 134 and electrodes 212.

In those embodiments in which stiffening element 208 is electricallyconductive, it is insulated from wires 252 and electrodes 212. It shouldbe appreciated, however, that stiffening element 208 may be formed fromany materials now or later developed.

Stimulator 134 is preferably encased within a housing that isimplantable within the recipient. The housing for the stimulator iscommonly implantable within a recess in the bone behind the earposterior to the mastoid. In one embodiment, lead 214 extends fromhandle member 212 to stimulator 134 or at least the housing ofstimulator 134. In one particular embodiment, lead 214 is continuous;that is, with no electrical connectors required to electrically connectelectrode assembly 200 to stimulator 134. One advantage of thisarrangement is that there is no requirement for a surgeon implantingelectrode assembly 200 to make the necessary electrical connectionbetween wires 252 extending from electrodes 212 and stimulator 134.

Holding member 1212 provides for improved handling, and to identifyelectrode orientation. As one of ordinary skill in the art wouldappreciate, in alternative embodiments, holding member 1212 may beconfigured as described in U.S. patent application Ser. No. 10/825,360,now U.S. Pat. No. 7,349,744, which is hereby incorporated by referenceherein in its entirety.

A profiled tip 210 is implemented in certain embodiments to guidecarrier member 202 during the insertion process, and to reduce friction.Alternative embodiments of tip region 210 are described in commonlyowned U.S. Provisional Patent Application No. 60/748,217 entitled“Promoting Curvature and Maintaining Orientation In An Electrode CarrierMember Of A Prosthetic Hearing Implant,” filed Dec. 8, 2005; U.S.Provisional Patent Application No. 60/748,274 entitled “ElectrodeCarrier Member For A Prosthetic Hearing Implant Having Optimal LengthFor Atraumatic Implantation,” filed Dec. 8, 2005; and U.S. ProvisionalPatent Application No. 60/748,317 entitled “Electrode Carrier Member ForA Prosthetic Hearing Implant Having Variable Pitch Electrodes ToFacilitate Atraumatic Implantation,” filed Dec. 8, 2005; all of whichare hereby incorporated by reference herein in the entireties. Inalternative embodiments, tip region 244 may be as described in U.S.patent application Ser. No. 10/825,358, published as U.S. PatentPublication 2004/0243212, now abandoned, and Ser. No. 11/125,171, nowU.S. Pat. No. 7,962,226, which are hereby incorporated by referenceherein in their entireties.

Collar member 204 serves as both a region for grasping electrodeassembly 200 and also acts to prevent insertion of carrier member 202beyond a predetermined maximum depth to reduce the risk of the surgeonover-inserting electrode assembly 200, which could otherwise causetrauma to the delicate structures of cochlea 132. In certainembodiments, the predetermined maximum depth is as described in theabove-referenced U.S. Provisional Patent Applications 60/748,217,60/478,274 and 60/748,317 and U.S. patent application Ser. Nos.10/518,811 and 11/125,171. Collar member 204 and band 206 are describedin further detail in the above applications.

In certain embodiments, carrier member 202 also includes a stiffeningmember 208 permanently embedded in at least proximal region 228 ofcarrier member 202. Stiffening member 208 is embedded, for example,during the manufacture of carrier member 202. As shown in FIG. 2A, theillustrative embodiment of stiffening member 208 extends from anextracochlear position through collar member 204 and into carrier member202. It should be appreciated that in alternative embodiments,stiffening member 208 need not be embedded in collar member 204, and anymay longitudinally extend further through carrier member 202 toterminate at any desired location along the length of carrier member202. As best shown in FIG. 2B, the distance that stiffening member 208extends into carrier member 202 is such that the stiffening memberterminates just before the lateral wall of the first turn of cochlea 132when carrier member 202 is completely inserted into cochlea 132.

Stiffening member 208 is configured to increase the stiffness of carriermember 202 in the region(s) 202 in which stiffness member 208 islocated. As such, stiffening member 208 assists in the prevention ofbuckling and/or deformation of carrier member 202 in such regions duringinsertion into cochlea 132. In particular, stiffener member 208 assistsin maintaining proximal region 228 of carrier member 202 in asufficiently straight configuration when subjected to the forcestypically experienced during implantation. This allows carrier member202 and electrodes 212 to be fully implanted into cochlea 132 withoutbeing subject to insertion forces that may damage the delicatestructures of the cochlea.

Additionally, stiffening member 208 causes electrodes 212 to bepositioned closer to the inner wall of cochlea 132, as generally astraight electrode will take a more lateral position in the basalregion. As a result, the distance from the stimulating surface ofcarrier member 202 to the auditory nerve endings is substantially lessthan would be the case if stiffening element 208 were not embedded inelectrode assembly 200. It is anticipated that this will provide similarbenefits in the basal region as a perimodiolar electrode, such as theperimodiolar electrode described in U.S. Pat. No. 6,421,569, which ishereby incorporated by reference herein. It should also be appreciatedstiffening the stiffness of member 208 may be less than, the same, orgreater than the stiffness of carrier member 202, so long as thepresence of stiffening member 202 in regions of carrier member 202results in at least one of such regions having a reduced likelihood ofdeformation.

FIGS. 3A through 3C are side views of different embodiments ofstiffening element 218, referred to herein as stiffening element 302A,302B, and 302C, respectively (generally and collectively referred to asstiffening element 302). Stiffening elements 302 are configured to beembedded in embodiments of electrode assembly 200, as noted above. Inthese embodiments, the stiffness or malleability of stiffening member208 is longitudinally varied so that, for example, distal portion 230 ofcarrier member 202 are more flexible than proximal portion 208. Suchvariability may be attained, for example, by annealing (FIG. 3A),tapering (FIG. 3B) or stepped reduction (FIG. 3C). In these and otherembodiments, there preferably is a gradual transition from the moreflexible distal end 304 to the stiffer proximal end 306 of the carriermember 202. It should be appreciated, however, that such a gradualtransition in the noted direction may be particular to the exemplaryapplication of cochlear implants and may vary differently in otherapplications.

Referring to FIG. 3A, stiffening element 302A is formed of, for example,glass or metal, which is annealed, i.e., subject to a process of heatingand slow cooling to toughen and reduce brittleness. In the embodimentshown in FIG. 3A, longitudinally adjacent regions 308 (only one isidentified for simplicity) of stiffening member 302A are subject todifferent annealing process, resulting in regions 308 having a differenthardness. In particular, longitudinally successive regions 309 haveincrementally greater or less flexibility, depicted in FIG. 3A bysuccessively increasing and decreasing widths of regions 308.

Referring to FIG. 3B, stiffening element 302B is, in this illustrativeembodiment, a unitary member that is tapered from its proximal end 306Btoward its distal end 304B. The reduced volume of material alongsuccessive regions of stiffening element 302 results in a successivelydecreasing stiffness. It should be appreciated that the rate of taperwill dictate the rate of change in flexibility of carrier member 202.

Referring to FIG. 3C, stiffening element 302C is an integrated elementcomprised of a plurality of elongate strips 310A-310D of differinglengths. Strips 310 may be formed of the same or different material, andmay be manufactured to have the same or different stiffness. Strips 310may be secured to each other or any manner now or later developed. Asshown in FIG. 3C, stiffening member 302C has a stepped configuration,due to the different lengths of strips 310. As such, the stiffnessprovided by stiffening member 302C varies due to the cumulativecontribution of each strip 310, which varies along its length. As one ofordinary skill in the art world would appreciate, strips 310 need not bearranged to form a continuous series of steps. For example, inembodiments in which the desired flexibility of carrier member 202 doesnot vary continuously, strips 310 may be configured such that, forexample, strip 310B is longer than strip 310C.

Advantageously, stiffening member 208 provides electrode carrier member202 with sufficient stiffness to allow it to be effectively insertedinto cochlear 132, particularly once carrier member 202 encounters someresistance beyond the first turn of the cochlea. A further advantage ofthe variation in stiffness is to ensure that electrode assembly 200 issuitable for all cochlea sizes. Cochlea sizes, and therefore the basallength, from the round window to the lateral wall of cochlea 132, varyslightly between recipients. The basal length is generally a straightpath and is usually in the order of approximately 4 mm to 7 mm. The moreflexible distal end of stiffening member 208 ensures that the distal tipof the stiffening member does not impact with the fragile structures ofthe cochlea. Rather, the distal end deforms allowing carrier member 202to curve whilst still ensuring the proximal region of the electrodearray 200 does not buckle or deform. Preferably, the variable stiffnessalso ensures that carrier member 202 forms a gradual curve rather than asharp bend that could result by having a sudden change in mechanicalstiffness.

In addition to the embodiments illustrated in FIGS. 3A-3C, the variablestiffness can be achieved by utilizing any number of the following aloneor in combination with each other or the embodiments described above: aplurality of stiffening members spaced at various pitches to provide avariable stiffness; use of different materials at various intervalsalong the length of stiffening member 208; varying dimensions ofstiffening element 308 or its component elements, etc. It should also beappreciated that stiffening member 208 can be of any manufacturablecross-section, including round, square, rectangular, oval etc., and useany manufacturable method to provide variable stiffness along itslength.

In alternative embodiments, stiffening element 208 extends further intocarrier member 202, providing regions of enhanced stiffness wheredesired. It should be appreciated that the regions of stiffness in theembodiments illustrated in FIGS. 3A-3C, or otherwise, need not varyregularly or consistently.

This stiffening arrangement may be similar to that described inAustralian Provisional Patent Application No. 2005904743, filed on 31Aug. 2005, and U.S. Provisional Application No. 60/748,273 filed Dec. 8,2005, which are hereby incorporated by reference herein in theirentireties.

All documents, patents, journal articles and other materials cited inthe present application are hereby incorporated by reference.

Although the present invention has been fully described in conjunctionwith several embodiments thereof with reference to the accompanyingdrawings, it is to be understood that various changes and modificationsmay be apparent to those skilled in the art. Such changes andmodifications are to be understood as included within the scope of thepresent invention as defined by the appended claims, unless they departtherefrom.

What is claimed is:
 1. An electrode array, comprising: a flexibleelongate carrier member configured to introduce a therapeutic elementinto a recipient, the carrier member including a proximal region and adistal region; and a stiffening element configured to: extendlongitudinally through at least a portion of the distal region of thecarrier member; and provide shape retention to at least a portion of thecarrier member.
 2. The electrode array of claim 1, wherein: theelectrode array is an electrode assembly of a prosthetic hearingimplant; the therapeutic element comprises a plurality of electrodesconfigured to stimulate auditory nerves of a recipient's cochlea; and aflexibility of the stiffening element is longitudinally varied along alength of the stiffening element.
 3. The electrode array of claim 2,wherein: a portion of the stiffening element extending through the atleast the portion of the distal region of the carrier member is moreflexible than another portion of the stiffening element extendingthrough the proximal region of the carrier member such that when thecarrier member is inserted into the cochlea, the stiffening element isconfigured to provide shape retention to the at least a portion of theproximal region of the carrier member.
 4. The electrode array of claim3, wherein the stiffening element is configured to maintain the at leastthe portion of the proximal region of the carrier member in asubstantially straight configuration during insertion of the carriermember into the cochlea.
 5. The electrode array of claim 3, wherein thestiffening element is configured to cause the plurality of electrodes tobe located relatively close to an inner wall of the cochlea wheninserted.
 6. The electrode array of claim 3, wherein the stiffeningelement is permanently embedded in the carrier member.
 7. The electrodearray of claim 3, wherein the flexibility of a portion of the stiffeningelement extending through the at least the portion of the distal regionof the carrier member is more flexible than the another portion of thestiffening element extending through the at least the portion ofproximal region of the carrier member.
 8. The electrode array of claim3, wherein longitudinally successive regions of the stiffening elementincrease in flexibility as a width of the stiffening element decreases.9. The electrode array of claim 3, wherein the flexibility of thestiffening element varies such that the proximal region of the carriermember is more flexible at a distal region of the proximal region than aproximal region of the proximal region.
 10. The electrode array of claim3, wherein the stiffening element is electrically conductive.
 11. Theelectrode array of claim 2, wherein the carrier member further comprisesa holding member connected proximal to the proximal region, the holdingmember configured to provide for improved handling by a personperforming said implantation.
 12. The electrode array of claim 11,wherein the holding member is further configured to identify a currentorientation of the electrode assembly.
 13. The electrode array of claim2, wherein: the carrier member comprises: a longitudinally-extendingmedial surface configured to face an inner wall of the cochlea wheninserted therein; and an opposing longitudinally-extending lateralsurface configured to face a lateral wall and a bony capsule of thecochlea when inserted therein; and the plurality of electrodes aredisposed on the carrier member such that a surface of each of theplurality of electrodes has an electrode surface that is at leastadjacent the medial surface of the carrier member when inserted in thecochlea.
 14. The electrode array of claim 13, wherein the electrodesurface of each of the plurality of electrodes is collocated with themedial surface of the carrier member.
 15. An electrode assembly of aprosthetic hearing implant, comprising: a flexible elongate carriermember configured to introduce a plurality of auditory nerve stimulatingelectrodes into a recipient's cochlea, the carrier member including aproximal region and a distal region, wherein the proximal regionextends, when inserted into the recipient's cochlea, from anextracochlear location to an intra-cochlear location; and a stiffeningelement configured to: extend longitudinally through at least a portionof the distal region of the carrier member; and provide shape retentionto at least a portion of the carrier member.
 16. The electrode assemblyof claim 15, wherein the stiffening element is configured such that,when the carrier member is inserted into the cochlea, the stiffeningelement extends from the extracochlear location to at least a portion ofthe distal region of the carrier member.
 17. The electrode assembly ofclaim 16, wherein the stiffening element is configured to maintain atleast a portion of the proximal region of the carrier member in asubstantially straight configuration during insertion of the carriermember.
 18. The electrode assembly of claim 16, wherein the stiffeningelement is configured to cause the plurality of electrodes to be locatedrelatively close to an inner wall of the cochlea when inserted.
 19. Anelectrode assembly of a prosthetic hearing implant, comprising: aflexible elongate carrier member configured to introduce a plurality ofauditory nerve stimulating electrodes into a recipient's cochlea, thecarrier member including a proximal region and a distal region, whereinthe proximal region extends, when implanted into the recipient'scochlea, from an extracochlear location to an intra-cochlear location;and a stiffening element configured to: extend longitudinally through atleast a portion of the distal region of the carrier member; and provideshape retention to at least a portion of the carrier member.
 20. Theelectrode assembly of claim 19, wherein the stiffening element isfurther configured to: resist deformation of the portion of the proximalregion from a substantially straight configuration; and cause theplurality of electrodes to be located relatively close to an inner wallof the cochlea when implanted.